Three years into a diversified, crash program to catch and surpass China and Russia in hypersonic missiles, the Air Force and the Department of Defense are beginning extensive prototype flight-testing and offering a first peek at their plans for large-scale production.
“We’ve got a series of up to 40 flight-tests planned for various hypersonic systems” over the next four years, said Mark Lewis, DOD’s director of defense research and engineering, in a February interview. Michael Griffin, undersecretary of defense for R&E, and Lewis’ boss, has designated hypersonics his top priority among 11 critical modernization technologies.
A Pentagon roadmap about how hypersonic missiles will be developed and built has recently been completed, and Congress “will get various versions” of it, ranging from unclassified to top secret, Lewis reported.
The roadmap lays out work by the military services, their research laboratories, the Defense Advanced Research Projects Agency, and others. It explains how “we want to move beyond prototyping … to delivered capability,” Lewis said. “That means taking the successful prototyping programs and getting them to effective, useful weapons. And by ‘effective,’ I mean not only capability, but numbers.”
The Pentagon has no interest in simply putting “a few weapons in tubes—we’re talking about a fully realized capability,” he added.
The first task is proving DOD’s chosen approaches can work and that they can be produced affordably and in significant numbers.
‘It’s essential that the Air Force not have single points of failure by relying on a sole supplier’ for hypersonic components.Will Roper, USAF’s acquisition chief
Pentagon acquisition chief Ellen Lord has created a hypersonics “war room,” she reported in March, chaired by Lewis and Assistant Secretary of Defense for Acquisition Kevin Fahey. Comprised of representatives from many offices within the Office of the Secretary of Defense, from industrial policy specialists to doctrine experts, the “war room” panel will assess whether the industrial base is able to produce supersonic-combustion ramjet engines, or scramjets; high-temperature materials; new guidance systems and other required items for hypersonics. It will also consider whether DOD has access to the personnel and expertise needed, and whether it should establish new relationships with universities to “identify talent.”
Working on a “pretty short-time fuse,” the team will have initial answers “in the next couple of months,” Lewis said.
Driving the effort is the fact that the U.S. has ceded the lead in hypersonics to its great power competitors, Russia and China. Those nations have surged ahead because the U.S. for too long “consistently made the decision to not transition” hypersonic technologies in the laboratory “to weapon applications,” Michael White, assistant director of hypersonics for R&E, said at a Pentagon press conference. Russia and China, however, did not hesitate, and that “got their efforts jump-started. And that’s what we’re accelerating now.” White added that the Pentagon leadership has decided “we can’t allow that asymmetry to stand.” America’s competitors have developed hypersonics in large part to “challenge … our domain dominance in space, on land, at sea, and in the air.”
He said the industrial plan is moving ahead early because “we’re looking to make critical investments in advanced techniques and capabilities that get affordability into the equation right from the start.”
Overall, the Pentagon has asked Congress to fund just over $3 billion for hypersonics research in fiscal 2021, including basic research and advanced prototyping.
DOD describes its hypersonics programs with terms like “medium” or “long” range. What does that mean?
“We’re very cautious about attaching numbers to exactly what we mean,” Lewis said in an interview. “All these systems wind up flying really long distances.”
For medium range, though, he said, “we’re talking about handfuls of hundreds of miles. Long range, we’re talking … a couple thousand nautical miles. It’s intentionally fuzzy.” The Pentagon, he said, is “still figuring out the concepts. That’s part of what we’re going to be exploring with our upcoming flight tests.”
White noted that the Conventional Prompt Strike program will be the first to fly, later this year. Wherever possible, the Pentagon will “accelerate our transition” from prototype to fielded capability. “We’re going to deliver to the warfighter as expeditiously as possible.”
When the Air Force halted the Hypersonic Conventional Standoff Weapon, or HCSW, in February, it effectively anointed its other system, the AGM-183 Air-Launched Rapid Response Weapon, or ARRW, as its first hypersonic missile.
Will Roper, the Air Force’s acquisition chief, said in a February press conference that the heavy load of big-ticket initiatives in USAF’s fiscal 2021 budget request—nuclear modernization, the Advanced Battle Management System, Joint All-Domain Command and Control, space superiority and the standup of the Space Force, to name a few—meant it couldn’t fund two boost-glide hypersonic missiles in parallel.
The ARRW is “more advanced” than HCSW, Roper said, and “unique.” By contrast, HCSW would have used the same hypersonic glide body as the Army and Navy systems. The resulting diversity of approaches will give adversaries more to worry about, he stated.
Lockheed Martin released two artist’s concepts of ARRW at the end of February. They portray a missile coming off a B-52 bomber pylon and flying up to a high altitude, at which point its aeroshell nose comes off, exposing the hypersonic glide vehicle within. Based on real photographs of the AGM-183 in captive-carry tests on a B-52, if the artist’s concept is correct, the hypersonic vehicle is probably only about five feet long.
“The reason we went with ARRW was not that HCSW was bad, but ARRW is smaller,” Roper said. “We can carry twice as many on a B-52.” The weapon might also be carried on the centerline station of the F-15, Roper added.
Both ARRW and HCSW are boost-glide hypersonic missiles, which use a rocket to push the glide body to hypersonic speed, after which the rocket motor is detached and the weapon glides and maneuvers to the target.
“I truly, truly hated to down-select between HCSW and ARRW a year early,” Roper said. Both were about to clear their critical design reviews (CDR) and would have yielded test flights this year. White said the Air Force is appropriately placing its’ “bet” on ARRW now, but HCSW will be put “on a shelf, and [we] can pull it off if we need it. But we want to focus our energies on ARRW to make sure that’s successful.”
The ARRW is “on track for an early operational capability in FY22,” an Air Force spokeswoman relayed in an email, confirming that it’s the only hypersonic prototyping effort the Air Force will fund in fiscal 2021. The USAF budget plan requests $382 million for hypersonics prototyping, down from the $576 million in this year’s budget.
A senior Air Force official confirmed that about $200 million left over from the HCSW effort will now be diverted to ARRW. Lockheed Space had been developing HCSW under a 2018 contract worth up to $928 million.
The DARPA program, called Tactical Boost Glide (TBG)—intended as a Mach 7 missile—was to serve as the basis of ARRW, but now the projects seem to be in parallel. John Varley, vice president for hypersonics at Lockheed Martin Missiles and Fire Control (MFC), said ARRW’s progress allowed it to pull even with the TBG effort.
The two projects were not intended to run in parallel, but had the company waited until all the work on TBG was complete, Varley said, “we wouldn’t be moving at the pace the customer’s looking for. … So, we’re going to learn. We’re going to fly TBG,” and incorporate discoveries into ARRW.
In the meantime, TBG will continue to do flight verifications, developmental testing, “inertial measurement testing, booster testing, and glide body testing. And we’re going to insert those lessons along the way.”
Prototype programs typically don’t have hardware built by the critical design review stage, he acknowledged, but “this is very mature.”
Varley acknowledged Lockheed has about $3.5 billion in hypersonics work across multiple divisions—MFC, Space, Skunk Works, and Aeronautics—and that the Pentagon has granted clearance to share information across those entities, which are governed by a company “hypersonics executive steering council.” Lockheed is the sole source on all but two of the major, acknowledged Defense hypersonics programs. The other principal contractor at the prime contractor level is Raytheon.
Regarding HCSW, Varley said he thinks the Air Force “made a very courageous decision—earlier than we thought [it would]—but we have to have the agility, as a corporation, to meet our customer’s changing demands. So, right now, ARRW is the Air Force’s main hypersonic program.”
Lockheed broke ground last September on a new facility in Courtland, Ala., close to the Army’s Huntsville, Ala., missile headquarters, that will ultimately be its hypersonic “center of excellence.” Varley said it will handle “all-up round integration, test, and buyout … so subsystems that will come across all our different business areas will end up there. We’ll do final integration, coding, testing, fueling, and ordnance assembly there.”
Longest Poles in the Tent
Five major challenges must be overcome for hypersonic weapons to become reality, Varley said:
- Managing Heat. With exterior temperatures rising to over 4,000 degrees Fahrenheit, the hypersonic vehicle must be strong enough to hold its shape, and guidance and communication electronics must be thermally hardened.
- Connectivity. At extreme temperatures, ionization may black out conventional communications, requiring sophisticated workarounds.
- Materials. Metal alloys and composite materials that can handle high heat loads must be developed. The vehicle will also require heat-resistant coatings.
- Maneuverability. Maneuvering at Mach 5-10 without causing the vehicle to tumble out of control will require delicate, autonomous handling.
- Accuracy. Extremely precise inertial measurement and other guidance systems will be essential, since a miss at hypersonic speed could put the vehicle far from its intended aimpoint.
Roper said that a further advantage to down-selecting to a single, rocket-boosted glide vehicle early means “we get to focus on producibility.”
The Pentagon “would like to get to dual suppliers, for both (ARRW and the Army/Navy systems), so that we don’t just succeed in flight-testing, we move into an industry base that’s capable of building at scale,” Roper said. That scale won’t be mass production, he added, “but we’d like a very adaptable, agile industry base that can allow us to do spiral upgrades, lot to lot.”
Choosing ARRW ahead of schedule lets the Air Force “start bringing on second suppliers a year earlier,” he explained.
One requirement will be an ability to 3D-print leading edges, Roper noted, because he believes refining that element of the design will require many iterations. It’s essential that the Air Force not have “single points of failure” by relying on a sole supplier for any key component.
In addition to ARRW, the Air Force and DARPA continue to pursue an air-breathing system called the Hypersonic Air-breathing Weapon Concept, or HAWC.
Viewed as a longer-term project, HAWC will require numerous advancements and is the type of problem Lewis calls “DARPA-hard.”
“They’re being very successful in that program,” Lewis said, “but the proof will be in their flight-test.”
Lewis said he has “more confidence in air-breathing at the tactical scale than the rocket-boost glide,” adding that he believes the nation needs both because “they bring different capabilities to bear.”
Air-breathing hypersonics weapons operate at lower altitudes and speeds. The Pentagon successfully tested the concept in the X-51 nearly 10 years ago, generating more than 200 seconds of air-breathing, hypersonic flight, Lewis noted. “So we know how to do this.”
Drawbacks of air-breathing hypersonic systems are that they require oxygen to combust with fuel, so they must operate at a lower altitude than rocket-boost glide systems. Moreover, their complex air intake geometries limit maneuverability, lest airflow be interrupted. The upside, though, is that they “don’t have to carry around an oxidizer,” Lewis said, so they can be lighter and smaller than rocket-powered alternatives, making them well-suited to air-launched applications.
“If you compare air-breathers to boost-gliders, you get more air-breathers for your dollar,” Lewis said. Air-breathers also can achieve “four to five times” the range of rocket-powered options at certain altitudes. White also noted that air-breathers have more room onboard for a terminal guidance capability and are “more affordable.”
The Pentagon is pursuing both technologies to diversify the problems U.S. forces present to adversaries, similar to operating a “high-low mix” of both F-15s and F-16s, Lewis asserted. “We use both, and in the way they perform best.”
Not all applications for hypersonics are medium or long range, he noted. For extremely short ranges and very long-range systems, the boost-glide is probably best, Lewis said. A rocket-powered, short-range missile—like a dogfight missile—can be “incredibly compact” and doesn’t need the volume required for an air inlet. It has a huge advantage in thrust to weight ratio and doesn’t need time to spool up to high speeds.
For “very, very long distances—say, a large fraction of the radius of the Earth—you … want to do it with a rocket,” Lewis said. For those missions, “what you really want to do is get out of the atmosphere and then get back in. …That’s why ICBMs are rocket-powered.”
For middle distances—“a couple hundred nautical miles to maybe a thousand miles … the air-breather is the better solution,” he said. “And that’s where we see the advantage in the hypersonic realm.”
The acquisition strategy is still being developed, White said. It’s in its early stages because the prototyping and experimentation phase is still underway. But the strategy will allow the Pentagon to “transition from [Research and Development] to weapon prototype. The transition to actual weapons … is where the acquisition strategy will come into play.”
Asked if hypersonics represent a potentially destabilizing technology, White opined that “it’s more destabilizing if [adversaries] have them, and we don’t.” Lacking such a capability, the U.S. would give up deterrence in a major area of competition, he said. “We have to be able to counter with similar capabilities when the time comes.”
Lewis said he does not expect the Pentagon’s hypersonics quest to narrow down to just a couple of programs.
“I don’t expect us to zero-in on just one or two things and stop there,” he predicted. “I expect development efforts to continue. … We have a very strong focus on delivering real capabilities, getting these things out of the laboratory … out of prototype and … into the hands of the warfighter, and that’s our primary focus now.”
Interservice Collaboration Continues
The Air Force’s Hypersonic Conventional Standoff Weapon was to have used the same gliding body as the Army’s Land-Based Hypersonic Missile and Navy’s Intermediate-Range Conventional Prompt Strike Weapon. Asked if USAF will continue to be involved in the other services’ efforts, Roper said collaboration will continue.
“We will certainly stay synched with them, on just the state of hypersonics in general.” Having a different approach “diversifies the number of flight bodies that are being looked at” in the Pentagon’s hypersonics portfolio, he said.
Lewis, in an interview, provided a little more background on the HCSW decision. The approach had some “very attractive features,” he said in an interview. That work was based on research already done by Sandia National Laboratories. Pentagon leaders reasoned, “ ‘wouldn’t it be great if we could leverage what they had done?’” and save some money by having some commonality of systems among the services, he said.
However, HCSW started turning into a modern version of the TFX/F-111 project of the 1960s, Lewis observed, in which both the Navy and Air Force tried to develop a common fighter-bomber. Compromises began to mount for both, and “you realize, maybe you’re not saving so much money, after all, and maybe it’s not such a great performer for your specific application,” Lewis explained.
The Air Force “came to the realization that the ARRW, derived from the DARPA tactical boost-glide program, for the specific Air Force application … was the better bet,” he asserted. “It was just a realization that although well-intentioned, the Air Force was better off investing in other areas, and we applaud them on that.” He added, “We have to be concentrating on the things we have the most confidence in.”
The HCSW decision isn’t a sign that USAF is backing away from hypersonics, Lewis said, but should be viewed instead as “an increase in the commitment. … It was a refocusing of their hypersonic efforts,” and a recognition that not all hypersonic projects now being explored “are going to become programs of record.”
While HCSW wasn’t the right solution for the Air Force, that doesn’t mean it’s not a good idea for the Army and Navy, Lewis noted. The decision to terminate HCSW was “more about the application; it wasn’t about the technology.” In OSD, “we’d rather see the services focus on what each one does best, so we’re frankly glad the Air Force is focusing on things that come off the wings of airplanes and come out of bomb bays; just as the Navy should be focusing on things that come out of tubes on ships.”